With the rapid growth of video and cloud services, operators pay much attention to flexibility of construction of optical networks, and reduction of construction and operation and maintenance costs of the optical networks. Network nodes need increasingly more cross-connect direction dimensions (or transmission paths). The operators may remotely and automatically perform dimension switching by using a reconfigurable optical add/drop multiplexer (ROADM) to replace a manner in which a person goes to a site to switch a connection of a fiber, so as to satisfy requirements on a dynamic network connection. In order to adapt to requirements on efficiency and flexibility of high-speed optical communications networks, the ROADM as a network cross-connect core needs to be developed constantly.
In a current ROADM node, using a discrete component is a common implementation form. A node is constructed through interconnection of multiple 1×M wavelength selective switches (WSS) to implement routing and switching selection of different signals. When a network service volume increases, a quantity of 1×M wavelength selective switches needs to be increased to improve a service switching capability of the node. However, it needs to add a large quantity of module slots in an existing device, so as to connect to multiple 1×M wavelength selective switches, and consequently, costs of the device are increased, and with an increase in a service volume, the costs are increased sharply.
At present, the 1×M wavelength selective switch is already relatively mature. However, there are no commercial products of N×M and N×N wavelength selective switches. Therefore, Fujitsu proposes a solution of an N×N WSS, as shown in FIG. 1. In this solution, a wavelength selective switch is provided with a fiber array, including four input fibers (11IN (#1) to 11IN (#4)) and four output fibers (11OUT (#1) to 11OUT (#4)), which are arranged in one column along one direction (a direction of a Y axis); and including eight collimators 12, a diffraction grating 1, a focusing lens 2, an input-side reflector (MEMS) array 3IN, and an output-side reflector (MEMS) array 3OUT, which are arranged in association with input and output fibers.
WDN light LIN (#1) to LIN (#4) output from the input fibers 11IN (#1) to (#4) are transmitted to the diffraction grating 1 by using the collimator 12, and is divided, according to wavelengths of the light, into wavelengths Ch1(#1) to ChN(#1), Ch1(#2) to ChN(#2), Ch1(#3) to ChN(#3), and Ch1(#4) to ChN(#4). Then, the wavelengths are focused by using the focusing lens 2, and are transmitted to the input-side reflector (MEMS) array 3IN.
The input-side reflector (MEMS) array 31N has 4×N MEMS reflectors 3IN(#1, Ch1) to 3IN(#1, ChN), 3IN(#2, Ch1) to 31N(#2, ChN), 31N(#3, Ch1) to 3IN(#3, ChN), and 3IN(#4, Ch1) to 3IN(#4, ChN). Reflective surfaces of the reflectors are located at a focusing position of the wavelengths passing through the focusing lens 2. Angles of the reflective surfaces are determined by wavelength routing setting information. Herein, the input-side reflector (MEMS) array 3IN is located at an angle of 45° relative to a direction of a Z axis.
The output-side reflector (MEMS) array 3OUT is arranged at an angle of −45° relative to the direction of the Z axis, and has 4×N MEMS reflectors 3OUT, (#1, Ch1) to 3OUT(#1, ChN), 3OUT(#2, Ch1) to 3OUT(#2, ChN) 3OUT(#3, Ch1) to 3OUT(3, ChN) and 3OUT(#4, Ch1) to 3OUT(#4, ChN), which are configured to enable the wavelengths reflected by the input-side reflector (MEMS) array 3IN to deflect in a direction towards a target output port.
After passing through the focusing lens 2, the reflected wavelengths are combined into WDM light LOUT(#1) to LOUT(#4) by the diffraction grating, and are coupled, by using the collimator 12, into the output fibers 11OUT(#1) to 11OUT (#4) for output.
In this solution, in order to implement an N×N cross function, the input-side reflector (MEMS) array and the output-side reflector (MEMS) array need to be calibrated at the same time, and are difficult to be commissioned.